The present invention relates to a thermoplastic welding rod used to join two pieces of thermoplastic sheeting together and more specifically a three dimensional welding rod used for joining thermoplastic sheets together.
In the coverings industry, it has been very desirable to achieve new and unique visuals in surface covering products. Many end-users find it desirable to heat weld flooring seams in an effort to prevent dirt and bacteria from entering the seams. One such method has been to heat weld seams with a solid-colored welding rod. In addition to aesthetic reasons, welding is popular in the healthcare industry where sanitation requirements are extremely important.
Flooring manufacturers often provide welding rods for seam sealing. Additionally, many wall systems are being marketed with seam welding or seam sealing materials. Seam welding rods are often an option to offer a decorative styling element to the specified job. Solid colored welding rods can either compliment the color of the patterned floor, or they can use an xe2x80x9caccentxe2x80x9d color that contrasts sharply with the floor to create a bold new look.
Only recently, however, has a manufacturer offered a multi-colored heat welding rod. The welding rod is a through-colored, patterned welding rod which matches the color and design of the floor covering pattern. This heat welding rod uses methods which create a through-color visual which extends all the way from the surface down through the entire depth of the composition in an uninterrupted fashion. The pattern is limited to a multi-colored, chip- or granule-image in which the chipped images are often distorted in the forming process and do not provide a field having any depth.
The use of an extruded, solid colored or clear, polyvinyl chloride, round cross-section welding rod is known in the art to join two pieces of vinyl resilient flooring together. Such processes often use an unfilled, highly plasticized, colored polyvinyl chloride formulation that is in turn extruded through a round die to form a round cross-section that is flexible and easily cut into a rod. However, a recent world patent WO 00/26004 describes a process for making welding rods with different shaped cross-sections.
Extrusion yields a solid color rod or some cases rods having shade variations such as a swirl effect. In no instance is a distinct sharp edge design obtained from an extruded welding rod. The solid color rod areas appear as a seam of solid contrasting color at every welded installation site creating a discontinuity in the flooring surface. This disrupts the flooring pattern image. This is especially so in the case of three dimensional flooring where particles or chips are covered by a clear plastic layer to give the appearance of a three dimensional floor. Extruded or printed pattern welding rods are unable to emulate the three dimensional flooring pattern. Thus, there is a need for a welding rod capable of producing a seam that will not disrupt the flooring pattern image of a three dimensional floor.
The present invention comprises both a method and composition for providing a three dimensional welding rod. The consolidated welding rod essentially comprises a first layer which is substantially formed from a layer having pigmented particles and a second layer which is substantially formed from a layer of transparent or translucent particles. The pigmented particles are typically larger than the clear particles such that the clear particles fill the void spaces between the larger pigmented particles. By filling the voids, the clear particles prevent the pigmented particles from being substantially distorted when the layers are consolidated. Preferably an excess amount of clear particles is provided to ensure a three dimensional visual. Thus, a three dimensional welding rod is provided whereby the pigmented particles appear to be dispersed about the clear particles and are not distorted.
In greater detail a three dimensional thermoplastic welding rod is provided having both a first and second layer. The first layer is formed form a material comprising pigmented particles, wherein the pigmented particles comprise a majority by volume of the first layer. The second layer formed is from materials comprising transparent or translucent particles. The second layer has an exposed surface opposite the first layer, the portion of the second layer adjacent the exposed surface comprising substantially all transparent or translucent particles.
In a further embodiment, the three dimensional thermoplastic welding rod comprising a first layer formed from a first material comprising a plurality of first particles. The second layer is formed from a second material comprising a plurality of second particles. The second layer has an exposed surface opposite the first layer and the transparency of the second layer is at least 30% greater than the transparency of the first layer.
Additionally included is a surface covering comprising at least two sheets joined together by a welded seam. The seam comprises a first layer formed from material comprising pigmented particles. The pigmented particles comprise a majority by volume of the first layer. The second layer is formed from material comprising transparent or translucent particles and has an exposed surface opposite the first layer. The portion of the second layer adjacent the exposed surface is comprised of substantially all transparent or translucent particles.
In an alternative embodiment, the surface covering comprises at least two sheets joined together by a welded seam. The welded seam has a first layer formed from a first material comprising a plurality of first particles and a second layer formed from a second material comprising a plurality of second particles. The second layer has an exposed surface opposite the first layer, the transparency of the second layer is at least 30% greater than the transparency of the first layer.
Further included is a method of forming a three dimensional thermoplastic welding rod. The method includes depositing a first layer comprising pigmented particles and depositing a second layer of transparent or translucent particles onto the layer of pigmented particles. The first layer and second layer are consolidated to form a welding rod.
In an alternative embodiment, a method of forming a surface covering is provided including welding at lest two sheets together using a thermoplastic welding rod comprising a first layer formed from material comprising pigmented particles. The pigmented particles comprise a majority by volume of the first layer. The second layer is formed from a material having transparent or translucent particles. The second layer has an exposed surface opposite the first layer. The portion of the second layer adjacent the exposed surface comprises substantially all transparent or translucent particles.